Macaque retroperitoneal fibromatosis (RF) is a proliferative disorder that has similarities to human Kaposi's sarcoma (KS). We have identified macaque subspecies-specific herpesviruses in RF tissue that are related to human herpesvirus 9, the etiological agent of KS. Follow-up of rhesus macaques naturally infected with RFHV and experimentally infected with SRV-2 indicated that these animals are immunologically abnormal, and established the tissue distribution of RFHV in infected animals. We have subsequently discovered another phylogentically distinct group of gamma herpesviruses in macaques. Analysis of tissues from wild-caught animals reveals that members of this group of viruses are also subspecies-specific, and that both groups of herpesviruses are found in macaques in the wild. FUNDING NIH grant RR00166. Bosch, M.L., Strand, K.B. and Rose, T.M. Gammaherpesvirus sequence comparisons. J. Virol. 72:9459-9459, 1999. Strand, K.B., Schmidt, A., Harper, E., Thormahlen, S.L., Wang, Y., Thouless, M., Birkebak, T., Morton, W.R., and Bosch, M.L. HHV-9-related gamma herpesviruses and disease in macaques. Abstr. 2nd Ann. AIDS Malignancy Conference, Bethesda, MD, April 6-9, 1999. Strand, K.B., Thormahlen, S., Harper, E., Rose, T.M., Tsai, C-C., and Bosch, M.L. Two distinct groups of KSHV-related gamma herpesviruses in macaques. Abstr. 1st Ann. Mtg. Kaposi's Sarcoma Assocated Herpesvirus (KSHV) and Related Agents, UC Santa Cruz, July 25-29, 1999. Bosch, M.L., Harper, E., Schmidt, A., Strand, K.B., Thormahlen, S., Thouless, M.E., and Wang, Y. Proliferative disorders associated with RFHV infection of rhesus macaques. Abstr. 1st Ann. Mtg. Kaposi's Sarcoma Assocated Herpesvirus (KSHV) and Related Agents, UC Santa Cruz, July 25-29, 1999.